Optical disc, reproduction apparatus, and disc identifier selecting apparatus

Abstract

An optical disc includes a processed area that has been processed by the irradiation of a YAG laser. Concave pits and convex pits having a length 3T–14T (T=0.133 μm) are formed in an area of the optical disc other than the processed area. The processed area includes (1) a concave pit having a length X or (2) a pit string that has a length X and includes a convex pit from which a reflection layer has been removed. A specific area of the optical disc records physical character information that shows the location and length of the concave pit or the pit string in the processed area.

1. An optical disc comprising:
 a processed area that has been processed with a laser, 
 wherein an area of the optical disc other than the processed area includes concave parts and convex parts, each of which has a length within a range from a first length to a second length and is coated with a reflection layer, and 
 the processed area includes a first concave part or a first pit string, the first concave part having a length exceeding the second length, and the first pit string having a length exceeding the second length and including concave parts and uncoated convex parts from which the reflection layer is removed. 
 
   
   
     2. The optical disc of  claim 1  further comprising a specific area,
 wherein the processed area further includes a second pit string that has a length exceeding the second length and includes a convex part on which a reflection layer having a length less than the first length exists, 
 the first concave part or the first pit string is distinguished from the second pit string by comparing a level of an RF signal obtained from the processed area with a first threshold value and a second threshold value, and 
 the specific area records information showing a location and a length of the first concave part or the first pit string. 
 
   
   
     3. The optical disc of  claim 2 ,
 wherein an RF signal obtained from the second pit string has a level that remains above the first threshold value but below the second threshold value, and 
 an RF signal obtained from the first concave part or the first pit string has a level that remains below both of the first threshold value and the second threshold value, 
 wherein the first threshold value is obtained by subtracting a predetermined offset from a certain threshold value used to convert an RF signal into a binary signal, and 
 the second threshold value is obtained by adding the predetermined offset to the certain threshold value.